1. Field of the Invention
The present general inventive concept relates to a method of manufacturing a color filter, and more particularly, to a method of manufacturing a color filter using an inkjet.
2. Description of the Related Art
Flat panel display devices having large screen sizes, such as liquid crystal displays (LCDs), plasma display panels (PDP), organic electro luminescence (EL), light emitting diodes, and field emission displays (FED) are today largely used. Among the flat panel display devices, the liquid crystal displays (LCDs), which are mainly used for computer monitors and notebook computer screens due to their low power consumption, are very popular.
The LCD includes a color filter for forming an image of a required color by filtering white light modulated by a liquid crystal layer. The color filter includes a plurality of red (R), green (G), and blue (B) pixels arranged in a predetermined pattern on a transparent plate. Examples of conventional methods of manufacturing a color filter are a dyeing method, a pigment dispersion method, a printing method, an electro-deposition method, and the like.
However, in the conventional methods of manufacturing a color filter, a predetermined process should be repeated for each color to form red (R), green (G), and blue (B) pixels, thereby decreasing the efficiency of the process and increasing the manufacturing cost.
Thus, recently, there has been proposed a method of manufacturing a color filter using an ink-jet, which is simpler and less expensive than the conventional methods. In the method of manufacturing the color filter using the inkjet, pixels of predetermined colors are formed by discharging ink drops of predetermined colors, for example, red (R), green (G), and blue (B) colors, in corresponding pixel areas on a plate of the color filter.
FIG. 1 is a diagram illustrating a conventional method of manufacturing a color filter 10 by discharging ink to form pixels of the color filter using an inkjet head 20. FIG. 2A is a graph illustrating a thickness of the ink discharged in pixel areas from a first nozzle 21 of the inkjet head 20 in FIG. 1 along a printing direction Y. FIG. 2B is a graph illustrating a thickness of the ink discharged in pixel areas from a fourth nozzle 24 of the inkjet head 20 in FIG. 1 along the printing direction Y. FIG. 3 is a diagram illustrating regions of the ink thicknesses illustrated in FIGS. 2A and 2B.
Referring to FIG. 1, the inkjet head 20 including a plurality of nozzles 21, 22, 23, and 24 discharges ink in each pixel area 11 while passing above the color filter 10 in the printing direction Y. The inkjet head 20 is tilted by a predetermined angle with respect to the color filter 10. After all pixel areas 11 along a column in the Y direction are filled with ink, the inkjet head 20 moves in a direction X, and then discharges ink into each pixel area 11 along an adjacent column in the direction Y. Remaining pixel areas 11 of the color filter 10 are filled with the ink by repeating the processes described above.
However, since the inkjet head 20 moves while being tilted by the predetermined angle with respect to the color filter 10, the amount of ink discharged from each of the nozzles 21, 22, 23, and 24 in pixel areas 11 at the beginning and end of the ink discharging process varies according to the number of nozzles discharging the ink.
Referring to FIGS. 1, 2A, 2B and 3, the amount of the ink discharged from the first nozzle 21 decreases gradually along the direction Y in a region I and is constant in a region II. The amount of ink discharged from the fourth nozzle 24 is constant along the direction Y in the region II and increases gradually along the direction Y in a region III.
The change in the amount of the discharged ink occurs since the number of nozzles passing through each region changes as the inkjet head 20 moves in the direction Y. In other words, in the region II, all of the four nozzles 21, 22, 23, and 24 discharge the ink, while the number of nozzles discharging the ink increases as the first nozzle 21, the second nozzle 22, the third nozzle 23, and the fourth nozzle 24 enter into the region I sequentially. On the other hand, in the region III, the number of nozzles discharging ink decreases as the fourth nozzle 24, the third nozzle 23, the second nozzle 22, and the first nozzle 21 exit the region III sequentially. Accordingly, the total amount of the ink discharged in the region I or III is more than that discharged in the region II.
The amount of discharged ink by each of the nozzles 21, 22, 23, and 24 varies based on the number of simultaneously operating adjacent nozzles since cross-talk between an operating nozzle and a non-operating nozzle occurs among the plurality of nozzles 21, 22, 23, and 24. In an opposite case, the total amount of the ink discharged in the region II may be more than that in the region I or III, as the amount of ink discharged by a nozzle decreases with an increase of nozzles simultaneously discharging ink.
The difference of the amount of the ink discharged from the same nozzle causes a difference in ink thicknesses in pixel areas, and accordingly, non-uniform thicknesses in some regions of the color filter occurs, thereby deteriorating the reliability of a color reproduction rate.